The effects of ecological rehabilitation on vegetation recruitment: some observations from the Wet Tropics of North Queensland

The nature of vegetation colonisation in four small rehabilitations and adjacent, protected control sites in tropical north Queensland were studied. Seven-year-old rehabilitation plots contiguous with forest had recruited up to seventy-two plant species across all growth forms and successional phases. Recruitment in 5-year-old plots was less abundant and diverse. Control sites by comparison were dominated by disclimax grasses and diversity of recruitment was reduced to only nineteen species at the upland control site. The effect of isolation on reducing abundance and diversity were demonstrated at one site located over,500 m from intact forest. Soil seed bank analysis was undertaken to examine any cumulative effect. Samples contained large numbers of weeds and grasses and only two native trees were recorded. The majority of species recorded in the plots were fleshy fruited zoochorous taxa, typical of plants in the early and intermediate stages of successional development, although a number of late successional species were also recorded. Fruit size and type suggests birds are responsible for most of the effective dispersal. The ability of ecologically rehabilitated areas to recruit and sustain new life forms is a true measure of their contribution to biodiversity conservation. In the tropics, the process of plant colonisation may be accelerated by establishing combinations of fleshy fruited native plant species from different stages of a normal forest succession, which attract seed dispersing birds and mammals. (C) 1997 Elsevier Science B.V.